This application claims priority from the German Application No. 198 15 185.3 filed on Apr. 4, 1998.
The invention relates to the field of automated electronically controlled printing presses and more particularly, means for ensuring reliability of computer controlled sheet-fed offset printing presses by efficiently potential and real shortcomings.
The course of development in printing technology continues to move away from separate optimization of mechanical and electronic components and increasingly follows the path of improving cooperation between these two divisions. Formerly, the field of printing press electronics could be described as being insular, i.e. the press is provided with printing plates, paper, ink and other consumer materials, and the role of electronics is confined to providing support for the mechanical components of the printing press. Thus, efforts to achieve better quality, shorter running times or reduction in spoilage, for example, are made by using a greater number of sensors and more intelligent electronics.
In this disclosure a computer-controlled printing press may be considered to include computer controllers, each such controller having processors, memory, BIOS and operating system as is usual and available. In addition, this computer controller has interfaces with the printing press hardware, whether in the form of sensors or actuators, and also a variety of diagnostic routines, control programs and interfaces with operators/maintenance-persons.
A typical printing press may have several printing units controlled by local electronic controllers, typically computers, and these local controllers may be in turn connected to a central computer or to each other. Alternatively, there may be a single central controller monitoring and managing several printing units. In either case, it is not unusual for each sensor or actuator to have at least one control and one data connection to an electronic control. Similarly, actuators require data and control lines so that the electronic controller may learn about the state of the device and command it to put into effect the desired action.
Typical sensors include devices for sensing position, rotational or linear velocity, acceleration, torsion, transmitted or reflected light, ink level detectors, temperature, voltage, current and connectivity detectors and the like. Similarly, actuators include ink dispensing devices, electric motors, magnetic devices, light emitting devices, heating/cooling devices, hydraulic devices, valves, switches and the like.
Now, electronics has advanced to the point of not just being a supporting player in the design and operation of printing presses, but being an integral part of printing presses. Printing presses of today have a very large number of sensors and actuators that have to be controlled precisely to deliver the high quality and economical products to which we have become accustomed.
A single printing unit may have as many as 20 to 54 ink adjusting units. There are several interfaces to send to and receive signals from a large number of actuators and sensors and to test for the integrity of the connections as well. Not surprisingly, electronic controllers may have to control several hundred sensors and actuators in course of loading printing plates, dispensing of ink, selection and feeding of paper and carrying out defined production runs with feedback controls on the quality of the printed product to ensure high quality and low cost.
However, this state of affairs also means that due to the increased complexity the cost of printing presses has been increasing as well. Such costs are realized both in the absolute cost of a printing press and the cost of breakdowns and maintenance associated with a complex piece of machinery.
A large number of sensors and procedures are designed to detect errors and fault conditions to avoid expensive damage and waste. Many patents describe systems for detecting such fault conditions. For example, U.S. Pat. No. 5,730,053, assigned to Man Roland Druckmaschinen AG of Germany, describes a bus system for an electronically controlled printing press such that the integrity of the bus system and its tolerance to signal strength is tested automatically. Even with specific mechanisms to diagnose and, on occasion, correct errors arising from improper cabling setup, cross-talk, wear and tear, component malfunction, gear play, slow response times and the like, printing presses remain susceptible to other errors.
Electronic controls contribute their own set of errors, in part, due to system complexity. It is not possible to test for the robustness of every possible configuration of each and every sensor and actuator. Furthermore, many software routines may have errors that come to light only when a particular task has to be performed. Not surprisingly, debugging of complex software to achieve perfect reliability is an unsolved problem at present.
Some software errors may be subtle enough that they do not justify disrupting a production run, but may still demand attention in order to optimize the operation of the printing press. Addressing such errors requires knowledge of the conditions that precipitated the particular error condition in order that special tools may be used to localize and correct the errors. An example of the peculiar difficulties presented by complex systems is the difficult to isolate and correct but, nevertheless, known coding error termed Y2K.
In other instances, efficient fault location and correction often requires a detailed knowledge of the configuration leading to the fault condition. Prior art does not provide tools and efficient mechanisms for collecting relevant configuration information.
EP 0 755 786 A1 discloses a means for controlling a printing machine. The ""786 application discloses a controller in a decentralized configuration and with the system having a common bus via which the various computers in the system communicate. Furthermore, a service computer can access the various control computers and perform checks and updates as needed via this bus as well. In the event of a program crash the cause of the crash may be investigated by using a special service computer, but with the disadvantage that the precise conditions leading to the crash cannot be replicated.
Another application, EP 0 728 581 A2, discloses a bus system in a printing machine where tests of the bus system are possible, even to the extent of determining the transfer reserve of the bus. But software errors are not easily analyzed in such a system because the testing is limited to the bus hardware capabilities, particularly when powering up.
Another application, EP 0 270 871 A2, describes a printing machine where the input or output signals of a digital control system may be examined separately. While the output circuit and faults therein can be monitored, and even errors due to cabling detected, the effect of such faults on the software is not readily detected. Furthermore, the printing press is still susceptible to faults due to a particular configuration.
The invention described herein overcomes these limitations in the prior art and provides for further improvements in printing presses and their operation.
The invention disclosed here comprises a software program called an interpreter-program for collecting data from a control computer or an interface even when the computer-controlled printing press is operating. The interpreter-program does not interfere with the real-time performance of either the printing press or the control computer and associated control programs. Furthermore, the interpreter-program is isolated from the rest of the control computer by means of run-time encapsulation thus permitting defined and rather limited access. This in turn reduces the chances of unforeseen errors and makes the system more robust.
Collecting data in course of actual operations is desirable since many of the expected errors, in particular software errors, may be expected to become noticeable in a particular configuration of the various components of the rather complex printing press. Thus, it is possible that a particular angle of a motor shaft in combination with a system configuration may have a tendency to enhance a possible error. Proper diagnosis of such an error would benefit from information about the precise configuration.
At the same time it is not desirable to monitor and store each and every possible state of the printing machine since this is both economically wasteful and impractical.
The interpreter-program is envisaged to be latent in most embodiments. It occupies a protected area of the system memory and is not active unless called upon to monitor some aspect of the printing press, such as an interface of interest. The activation of the interpreter-program may be via an interface to the interpreter-program and may be effected by either an operator or a system fault and the like depending on the particular embodiment. The functions of the interpreter-program may be better understood by the following description of some of the many benefits made possible by the invention.
It is an object of this invention to collect information from specified interfaces to facilitate monitoring in a computer-controlled printing press.
It is another objective of this invention to collect information from specified interfaces to facilitate fault detection in a computer-controlled printing press.
It is another objective of this invention to collect information from specified interfaces in a computer-controlled printing press to facilitate fault localization.
It is another objective of this invention to collect information from specified interfaces in a computer-controlled printing press without adversely affecting the real-time functioning of the printing press.
It is another objective of this invention to collect information from interfaces in a computer-controlled printing press to provide data for simulating the operation of the printing press.
It is yet another objective of this invention to collect data about the state of the control programs without modifying the runtime environment of the control programs.
It is yet another objective of this invention to permit execution of a run-time encapsulated diagnostic program in a computer-controlled printing press while the printing press is functioning.
It is yet another objective of this invention to facilitate collection of data pertinent to the state of a computerized controller in a computer-controlled printing machine for subsequent analysis on another special purpose computer or by another program.
It is yet another objective of this invention to facilitate collection of relevant data in a distributed control system for a printing press.
It is yet another objective of this invention to facilitate investigations into the state of selected parts of a printing press to further optimize the operation of printing presses.
It is yet another objective of this invention to facilitate service calls while a printing press is in operation.